With most long distance passenger service having been taken away by the airlines, after World War Two, the railroads were forced to emphasize freight service. More powerful diesel locomotives were built and pneumatic brakes became standard equipment. The freight trains became longer and heavier and at the same time slower.
While passenger service has been taken away by the airlines, freight service to a large extent is being taken away by trucks, which have been able to travel at faster average speeds. The average freight train speed is 20.1 miles per hour, when calculated by dividing total train miles by total train hours; in spite of the slow speed a number of catastrophic train disasters occurred last year. After all, the rate of retardation of a train by its braking system depends upon the wheel-rail adhesion, which is very limited on regular rails. It cannot prevent wheel sliding.
Revitalizing the railroads requires an increase in performance, i.e., in powered acceleration and braking deceleration, which requires improved derailment protection and additional traction, as well as improved safety over track joints, curves and switches.
Many systems have been proposed to solve these problems. Multi-rail systems are described for example in U.S. Pat. Nos. 3,988,166 and 188,611. Spring-loaded guide wheels are shown in U.S. Pat. No. 861,830 and in German Offenlegungsschrift 2,226,462.
None of the prior systems provide the necessary combination of changes required to attain the highest level of performance and safety, utilizing the presently existing systems.